use video stream interlaced flag to enable/disable deinterlacing

Description

This patch use the interlaced_frame flag returned by ffmpeg/libmpeg2 to enable/disable the deinterlacer. In addition, since the flag can be incorrect, it adds a deinterlace mode entry to the OSD menu to force the deinterlacer on or off (or return to autodetect). There is also a CYCLEDEINTERLACE keybinding, though it has no default key.